Polish prosecutors on November 14 began the exhumation of President Lech Kaczynski, who was killed in a plane crash in Russia in 2010.

They are examining his remains as part of a renewed investigation into the crash near Smolensk in western Russia that killed 96 people -- including Kaczynski’s wife, Poland’s top military leadership, and the governor of Poland’s central bank.

An investigation by Poland’s previous, centrist government ruled that the crash of the government’s Soviet-made TU-154 airplane in heavy fog during an attempt to land was the result of pilot error.

But Kaczynski’s twin brother, Jaroslaw, has said an onboard explosion could have caused the crash.

Prosecutors also want to determine whether there was a mix-up of remains during burial and whether the bodies were described correctly in previous investigations.

They say Russia’s refusal to return the plane wreckage is a critical obstacle.

Jaroslaw Kaczynski’s nationalist Law and Justice Party unseated the centrists in 2015 elections.